Ik rig severely deforms, target pole rotates torso?
I think what had happened was that there were as I suspected, weighting issues, hierarchial problems and bones had been edited in the wrong mode which can cause problems with the set rotation, scale and location in pose mode.

Here I've given you an example of a rigify rig which comes with names and and logical hierarchy. It will need weight painting to fix deformations of limbs but it'll give you a head start.

https://www.dropbox.com/s/2xhietllb671q0k/posed%20girl_edit.blend?dl=0

Good luck with it